The present invention relates to an apparatus and method for optical evaluation suitable for use in in-line property evaluation performed in the process of manufacturing a semiconductor device, to an apparatus and method for manufacturing a semiconductor device utilizing optical evaluation, a method of controlling the apparatus for manufacturing a semiconductor device, and a semiconductor device to be subjected to optical evaluation.
As ever-higher integration has been achieved in recent semiconductor integrated circuits, increasing miniaturization and higher performance have been required of a transistor element to be mounted on a MOS semiconductor device. In particular, the increasing miniaturization of the transistor element has created the demand for a MOS device having high reliability. To implement the MOS devices having high reliability, however, each component of the MOS device should have high reliability.
For example, the reliability of a contact portion, which is dependent on a method of forming a contact window, is an important factor in determining the reliability of such a MOS device. When a damaged layer is produced in a semiconductor substrate by dry etching performed to form the contact window, it is removed by wet etching subsequent to the dry-etching process. To estimate the proper amount of removal, a conventional method of manufacturing a semiconductor device has used a wafer for monitoring, not for products, to measure the electric property thereof and thereby determine the depth of the damaged layer produced during the dry-etching process. The wet-etching process for removing the damaged layer is performed under such conditions as a duration of time and a temperature that have been determined based on the electric property. Thus, the conventional method of manufacturing a semiconductor device has optimized processing conditions during the manufacturing process based on the electric property obtained by using the wafer for monitoring.
In the process of forming the individual components of a semiconductor device, the technology of impurity introduction, e.g., plays an important role in determining the operational properties of the semiconductor device. Ion implantation is a predominant method for impurity introduction, whereby impurity ions from ion source are accelerated with the application of an electric field and thereby allowed to enter a semiconductor substrate or an electrode. During the ion implantation, impurity ions are normally accelerated with energy of several tens of kiloelectron volts before entering the semiconductor substrate or the like. However, the implantation of the impurity ions has caused a crystallographically damaged layer in the surface of the semiconductor substrate or the like. In addition, the impurity has not been activated as carriers, while the concentration of the impurity has not optimumly been distributed. For the activation of the impurity, recovery from the damage, and optimization of profiles, a heat treatment (annealing) has typically been performed after ion implantation. Conventionally, the annealing process time, temperature, and the like have been determined through the optimization of design (device simulation) and conditions. In principle, conditions for annealing have been determined empirically. In particular, an annealing process for recovery from the surface damaged layer of the semiconductor substrate has been performed empirically.
As for a gate insulating film used in a MOS device, the thickness thereof has increasingly been reduced at a high pace, so that an extremely thin insulating film with a thickness of 4 nm or less will probably be used in the 21st century. in a MOS device having such an extremely thin insulating film, the properties of the insulating film may determine the properties of the entire CMOS device and hence the electric property of the whole semiconductor integrated circuit. Therefore, the properties of the insulating film are considered to be particularly important.
The properties of such a gate insulating film have conventionally been controlled by forming a MOS capacitor or MOS transistor and evaluating the electric property thereof. The evaluation of the electric property is performed during or after the manufacturing of a MOS device by retrieving a wafer with the MOS device mounted thereon from a chamber.
With the increasing miniaturization of the MOS device as described above, the conventional evaluation method has presented the following problems in the processes of etching, introducing an impurity, and forming a gate insulating film.
First, the etching process has the following problems. While the two-dimensional size (horizontal size) of the contact window has been reduced increasingly, the depth of the contact window has not been reduced, resulting in an increased aspect ratio (ratio of the depth to the horizontal size). To form such a contact window with a high aspect ratio, a high-vacuum/high-density plasma has been used in, e.g., a dry-etching process. The high-vacuum/high-density plasma process has successfully formed a deep contact window by using high-energy ions in vertical directions. However, the bombardment of the high-energy ions has caused a more seriously damaged layer having a greater depth in the semiconductor crystal of the bottom of the contact window than has been caused by conventional dry etching using a comparatively low-vacuum/low-density plasma. In the case of using light of a wavelength in the microwave range (such as an infrared ray) to evaluate a damaged layer, light itself enters the Si substrate and reaches a point at a depth of more than 1 xcexcm from the surface thereof, so that it is impossible to precisely evaluate damage on a level of several tens of nanometer caused actually by the plasma to the Si substrate. In spite of the future trend toward an increasingly miniaturized LSI, it has become substantially impossible to accurately evaluate a thin damaged layer formed only at the surface as well as an extremely miniaturized region.
Hence, it has become difficult to ensure the removal of the damaged layer with excellent controllability by using only the conventional evaluation method.
Next, the impurity introducing process and the annealing process have the following problems. With the miniaturization of individual elements in a semiconductor device, profile control as well as impurity introduction in a miniaturized region has played an increasingly important role. However, in accordance with the conventional method in which annealing conditions are set empirically, optimum profiles cannot be obtained or trouble occurs oftentimes as a result of terminating the process with a defect remaining in a semiconductor substrate. Moreover, a developing efficiency will be reduced significantly if annealing conditions are optimized by the conventional procedure consisting of processing and analysis repeatedly performed in this order, while a shorter period of time is required to develop a desired semiconductor device. Under such circumstances, process control technology using an in-situ observation technique for the annealing process has been in recent demand. In performing heat treatment by using single-wafer heat treatment apparatus, slight variations are observed in the amount of heat treatment performed with respect to different wafers. The variations may be attributed to the properties of the single-wafer heat treatment apparatus which are intrinsically different or have varied with time, unlike conventional heat treatment apparatus for batch processing. Furthermore, it is also difficult to precisely determine an actual dose for impurity introduction and the effective concentration of the impurity introduced into the substrate after heat treatment.
Th process of forming a gate insulating film has the following problem. In the case of controlling the properties of the gate insulating film by the conventional method of evaluating the electric property, even when any trouble occurs in the process of forming the insulating film, the trouble will be discovered only after the wafer is retrieved from the chamber after the completion of the process and the electric property thereof is evaluated. Until then, the gate insulating film having the trouble will have been manufactured without interruption, resulting in a reduced productivity (efficiency).
It is therefore a first object of the present invention to provide an apparatus and method for optical evaluation which ensure the in-line sensing of the foregoing factors influencing the properties of a semiconductor device in the manufacturing process and implement a semiconductor device having excellent and consistent properties.
A second object of the present invention is to provide a method and apparatus for manufacturing a semiconductor device wherein in-line control is exerted over various types of processing performed with respect to the semiconductor device by focusing attention on the correlation between the optical property of a semiconductor region and the state thereof and using the result of evaluating the optical property.
A third object of the present invention is to provide a method of controlling an apparatus for manufacturing a semiconductor device wherein maintenance is performed with respect to a chamber of the apparatus for manufacturing a semiconductor device by using a varying accuracy with which an optical property is evaluated.
A fourth object of the present invention is to provide a semiconductor device having a structure suitable for the evaluation of optical property.
To attain the first object, the present invention has proposed first and second optical evaluation apparatus as well as an optical evaluation method.
To attain the second object, the present invention has proposed an apparatus for manufacturing a semiconductor device and first to fifth methods of manufacturing semiconductor devices.
To attain the third object, the present invention has proposed a method of controlling an apparatus for manufacturing a semiconductor device.
To attain the fourth object, the present invention has proposed a semiconductor device.
A first optical evaluation apparatus according to the present invention is for use in processing a substrate having a semiconductor region in a chamber, the apparatus comprising: a first light source for generating exciting light; a second light source for generating measurement light; a first light guiding member for intermittently supplying the exciting light generated from the first light source to the semiconductor region of the substrate in the chamber; a second light guiding member for supplying the measurement light generated from the second light source to the semiconductor region; reflectance measuring means for measuring a reflectance of the measurement light supplied to the semiconductor region; a third light guiding member for causing the measurement light reflected from the semiconductor region to be incident upon the reflectance measuring means; and change calculating means for receiving an output from the reflectance measuring means and calculating a change rate of the reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
The use of the optical evaluation apparatus achieves the following effect. When the semiconductor region is irradiated with the exciting light guided by the first light guiding member, carriers in the semiconductor region are excited to form an electric field. Due to the electric field, the reflectance of the measurement light guided by the second light guiding member to the semiconductor region changes in the presence and absence of the exciting light. The change rate varies depending on the intensity of the electric field and on the wavelength of the measurement light. If the semiconductor region contains a defect forming a center of recombination for carriers, the lifetimes of the excited carriers are reduced so that the electric field formed by the carriers has a reduced intensity. In other words, the change rate of reflectance in the presence and absence of the exciting light changes depending on the number of defects in the semiconductor region or the like, so that the change rate of the reflectance of the measurement light in the semiconductor region which has been calculated from the value measured by the reflectance measuring means reflects the crystallographic state of the semiconductor region or the like. Consequently, it becomes possible to control conditions for processing performed in the chamber based on the result of in-line evaluation performed with respect to the semiconductor region.
Preferably, the second light guiding member causes the measurement light to be incident upon a surface of the substrate in a direction approximately perpendicular thereto.
In the arrangement, since the measurement light is directed to the surface of the semiconductor substrate in a direction approximately perpendicular thereto, a change in the reflectance of light from a small semiconductor region can be evaluated promptly and accurately. The resulting optical evaluation apparatus enables optical evaluation in the process of manufacturing an increasingly miniaturized semiconductor device.
Preferably, the first light guiding member causes the exciting light to be incident upon the surface of the substrate in a direction approximately perpendicular thereto.
There may further be provided optical axis adjusting means for guiding the exciting light and the measurement light onto a common optical axis before the exciting light and the measurement light is supplied to the semiconductor region and the second light guiding member may be composed of a mirror for supplying the measurement light and exciting light, each guided onto the common optical axis by the optical axis adjusting means, to the surface of the substrate in a direction approximately perpendicular thereto and upwardly transmitting the measurement light and exciting light reflected from the semiconductor region.
In the arrangement, the measurement light and the excited light are supplied to the surface of the semiconductor region in a direction approximately perpendicular thereto. Consequently, even when the semiconductor region has an extremely small area, it becomes possible to perform optical evaluation using the change rate of the reflectance of the measurement light. What results is an optical evaluation apparatus particularly suitable for real-time monitoring of processing performed in the semiconductor region.
There may further be provided spectroscopic means for receiving the measurement light reflected from the semiconductor region, separating the measurement light, and sending the separated measurement light to the reflectance measuring means.
This provides information on a wide range of wavelengths of the measurement light and enables the change rate of the reflectance of the measurement light of appropriate wavelengths to be used depending on the type of processing performed in the chamber.
The first and second light sources may be composed of a single common light source for generating a wide spectrum of light of wavelengths including wavelengths of the exciting light and wavelengths of the measurement light, the apparatus may further comprise: a beam splitter for splitting the wide spectrum of light generated from the common light source into the exciting light and the measurement light; and spectroscopic means for receiving the measurement light reflected from the semiconductor region, separating the measurement light, and sending the separated measurement light to the reflectance measuring means, and the first and second light guiding members may be placed in such a position as to receive the light from the splitter.
Since only one light source is sufficient, the optical evaluation apparatus has an extremely simple structure.
The change calculating means may calculate only the change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light.
The arrangement enables the detection of a change in the reflectance of the measurement light of a most desired wavelength, resulting in a highly sensitive optical evaluation apparatus with no noise.
There may further be provided a filter for receiving the measurement light reflected from the semiconductor region, transmitting only the measurement light of a wavelength in a specified range, and sending the transmitted measurement light to the reflectance measuring means.
The arrangement enables the detection of a change in the reflectance of light of desired wavelengths without spectroscopic means, so that the resulting optical evaluation apparatus has a simpler structure and performs low-noise optical evaluation with high sensitivity.
Preferably, the specified energy value of the measurement light is any value included in a range of 3.2 to 3.6 eV.
The reflectance measuring means measures the reflectance of the light of a wavelength of preferably 600 nm or less, and more preferably, 300 to 600 nm.
Preferably, the first light guiding member intermittently emits the exciting light at a frequency of 1 kHz or less.
The apparatus may be constituted by using an ellipsometric spectroscope.
In the arrangement, the components of the ellipsometric spectroscope typically added to the chamber of the apparatus for manufacturing a semiconductor device can be utilized, resulting in an optical evaluation apparatus with less additional cost.
A second optical evaluation apparatus according to the present invention is for evaluating an electric property of an insulating film formed on a semiconductor region of a substrate, the apparatus comprising: a first light source for generating exciting light; a second light source for generating measurement light; a first light guiding member for intermittently supplying the exciting light generated from the first light source and transmitted by the insulating film to the semiconductor region immediately under the insulating film; a second light guiding member for supplying the measurement light generated from the second light source and transmitted by the insulating film to the semiconductor region intermittently supplied with the exciting light; reflectance measuring means for measuring a reflectance of the measurement light supplied to the semiconductor region; a third light guiding member for causing the measurement light reflected from the semiconductor region to be incident upon the reflectance measuring means; change calculating means for receiving an output from the reflectance measuring means and calculating a change rate of the reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light; and evaluating means for evaluating the electric property of the insulating film based on the change rate of the reflectance of the measurement light.
With the arrangement, information on an electric defect in an insulating film, particularly a gate insulating film, can be obtained. Specifically, when the semiconductor region is irradiated with the exciting light, carriers are excited and an electric field changes as the number of carriers changes, so that the reflectance of the measurement light of a given wavelength from the semiconductor region changes. If an insulating film is formed on the semiconductor region, however, the change rate of the reflectance of the measurement light is lowered since a defect site for trapping carriers is present in the surface layer of the semiconductor region. However, an increase in the intensity of the electric field in the adjacent semiconductor region is increased, which increases the change rate of the reflectance of the measurement light. Therefore, the electric property of the insulating film can be controlled promptly and reliably by judging the quality of the insulating film if the reflectance of the measurement light falls outside the specified range.
The evaluating means may judge the insulating film to be good only when the change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light corresponds to a proper capacitance value of the insulating film.
The specified energy value of the measurement light may be any value included in a range of 3.2 to 3.6 eV.
In this manner, optical evaluation is performed at a point in the spectrum of the change rate of the reflectance in a characteristic configuration at which a difference in electric property of the insulating film is detected most sensitively.
There may further be provided spectroscopic means for receiving the measurement light reflected from the semiconductor region, separating the measurement light, and transmitting the separated measurement light to the reflectance measuring means.
The arrangement provides a spectrum of the change rate of the reflectance of the measurement light, so that it becomes possible to perform optical evaluation with high precision based on the information on the whole spectral configuration.
There may further be provided a filter for receiving the measurement light reflected from the semiconductor region, transmitting only the measurement light of a wavelength in a specified range corresponding to the specified energy value of the measurement light, and sending the transmitted measurement light to the reflectance measuring means.
The arrangement enables the detection of a change in the reflectance of light of desired wavelengths without spectroscopic means, so that the resulting optical evaluation apparatus has a simpler structure and performs prompt optical evaluation.
The reflectance measuring means measures the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm.
The arrangement allows optical evaluation to be performed based on the change rate of the reflectance of the measurement light only from the portion of the semiconductor region susceptible to the influence of trapped electrons contained in the insulating film by using the fact that the measurement light of a wavelength in the visible region or a shorter wavelength does not reach a portion deeper than several hundreds of nanometers from the surface of the semiconductor region.
The apparatus may be constituted by using an ellipsometric spectroscope.
The arrangement allows the optical evaluation apparatus to be constituted at low cost by using the ellipsometric spectroscope used to measure the thickness of a gate oxide film or the like.
Preferably, the apparatus is attached to a chamber used to form an oxide film for a semiconductor device.
The arrangement allows the quality of the insulating film to be evaluated without recovering the semiconductor substrate from the manufacturing apparatus, resulting an evaluation apparatus suitable for in-line property evaluation.
The second light source may be an Xe lamp.
The first light source may be an Ar ion laser or a He-Ne laser.
Preferably, the first light guiding member intermittently emits the exciting light at a frequency of 1 kHz or less.
An apparatus for manufacturing a semiconductor device according to the present invention comprises: a chamber for containing a substrate having a semiconductor region; processing means for performing processing with respect to the substrate in the chamber; first light supplying means for intermittently supplying exciting light to the semiconductor region of the substrate placed in the chamber; a second light supplying means for supplying measurement light to the semiconductor region; reflectance measuring means for measuring a reflectance of the measurement light supplied to the semiconductor region; change calculating means for receiving an output from the reflectance measuring means and calculating a change rate of the reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light; and processing control means for receiving an output from the change calculating means during the processing performed by the processing means and controlling a condition for the processing based on the change rate of the reflectance.
The use of the apparatus for manufacturing a semiconductor devices achieves the following effect. When the semiconductor region is irradiated with the exciting light supplied by the first light supplying means, carriers are excited to produce an electric field. Due to the electric field, the reflectance of the measurement light supplied by the second light supplying means changes in the presence and absence of the exciting light supplied. The change rate varies depending on the intensity of the electric field and on the wavelength of the measurement light. If the semiconductor region contains a defect forming a center of recombination for carriers, the lifetimes of the excited carriers are reduced so that the electric field formed by the carriers has a reduced intensity. In other words, the change rate of reflectance in the presence and absence of the exciting light changes depending on the number of defects in the semiconductor region or the like, so that the change rate of the reflectance of the measurement light in the semiconductor region which has been calculated from the value measured by the reflectance measuring means reflects the crystallographic state of the semiconductor region or the like. Moreover, since the processing control means controls conditions for processing performed in the chamber based on the result of in-line evaluation performed with respect to the semiconductor region, the resulting semiconductor device has desired properties.
The processing means may generate a plasma in the chamber and perform etching with respect to the semiconductor region by using the generated plasma.
This enables the depth of a damaged layer and the degree of damage caused by etching to be controlled, so that the subsequent removal of the damaged layer is performed smoothly.
The processing means may generate a plasma in the chamber and perform light dry etching by using the generated plasma so as to remove a damaged layer caused by etching performed with respect to the semiconductor region.
This enables the depth of a damaged layer and the degree of damage caused by etching to be controlled and light dry etching to be performed to remove the damaged layer.
The processing means may introduce an impurity into the semiconductor region.
This enables the number of defects caused by the introduction of the impurity and the level of defectiveness to be controlled.
The processing means may perform annealing after impurity ions are implanted in the semiconductor region.
This enables annealing for removing the structural disorder caused by impurity ions completely and efficiently.
The processing means may form a thin insulating film on the semiconductor region.
This enables an insulating film having desired properties such as a gate oxide film to be formed.
When a thin insulating film has been formed on the semiconductor region, the processing means may perform dry etching to remove the insulating film from a top surface of the semiconductor region.
This enables the progression of the process of removing the insulating film to be controlled based on the result of in-line optical evaluation by using the fact that the change rate of the reflectance of the measurement light from the semiconductor region is influenced by the thickness of the insulating film.
Preferably, an angle formed between the measurement light supplied by the second light supplying means and a surface of the substrate is larger than an angle formed between the exciting light supplied by the first light supplying means and the surface of the substrate.
This enables the measurement light to be supplied to a smaller area. As a result, the area of the semiconductor region necessary for measuring the reflectance of the measurement light can be reduced.
The second light supplying means may supply the measurement light to a surface of the substrate in a direction approximately perpendicular thereto.
In the arrangement, the measurement light is supplied to the semiconductor wafer in a direction approximately perpendicular thereto. Consequently, even when the semiconductor region has an extremely small area, it is possible to easily perform optical evaluation, which reduces a useless space for optical monitoring and improves sensitivity, resulting in a significantly reduced time required to evaluate an optical property.
Preferably, the first light supplying means supplies the exciting light to the surface of the substrate in a direction approximately perpendicular thereto.
Preferably, the first light supplying means intermittently emits the exciting light at a frequency of 1 kHz or less.
The second light supplying means and the reflectance measuring means may be constituted by using an ellipsometric spectroscope.
In the arrangement, the components of the ellipsometric spectroscope typically added to the chamber of the apparatus for manufacturing a semiconductor devices can be utilized, so that it becomes possible to control processing based on the result of in-line optical evaluation, while suppressing an increase in cost.
An optical evaluation method according to the present invention is for evaluating processing performed with respect to a substrate having a semiconductor region in a chamber, the method comprising the steps of: supplying measurement light to the semiconductor region of the substrate in the chamber; intermittently supplying exciting light to the semiconductor region; and calculating a change rate of a reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
In accordance with the method, carriers in the semiconductor region are excited when the semiconductor region is irradiated with the exciting light and produce an electric field. Due to the electric field, the reflectance of the measurement light supplied to the semiconductor region changes in the presence and absence of the exciting light. The change rate varies depending on the intensity of the electric field and on the wavelength of the measurement light. If the semiconductor region contains a defect forming a center of recombination for carriers, the lifetimes of the excited carriers are reduced so that the electric field formed by the carriers has a reduced intensity. In other words, the change rate of reflectance in the presence and absence of the exciting light changes depending on the number of defects in the semiconductor region or the like, so that the change rate of the reflectance of the measurement light in the semiconductor region which has been calculated reflects the crystallographic state of the semiconductor region or the like. Consequently, it becomes possible to control conditions for processing performed in the chamber based on the result of in-line evaluation performed with respect to the semiconductor region.
Preferably, the measurement light is supplied to a surface of the substrate in a direction approximately perpendicular thereto in the step of supplying the measurement light.
The method allows optical-modulation reflectance spectrophotometry to be performed also with respect to a semiconductor region having a small area.
Preferably, the exciting light is supplied to the surface of the substrate in a direction approximately perpendicular thereto in the step of supplying the exciting light.
The processing may be a plasma etching process performed with respect to the semiconductor region.
This enables the depth of a damaged layer and the degree of damage caused by etching to be controlled, so that the subsequent removal of the damaged layer is performed smoothly.
The processing may be a light dry etching process for removing a damaged layer caused by plasma etching performed with respect to the semiconductor region.
This enables the depth of a damaged layer and the degree of damage caused by etching to be controlled and light dry etching to be performed to remove the damaged layer.
The processing may be a process of introducing an impurity into the semiconductor region.
This enables the number of defects and the level of defectiveness caused by the introduction of the impurity to be controlled.
The processing may be an annealing process performed after impurity ions are implanted in the semiconductor region.
This enables annealing to be performed to remove the structural disorder caused by impurity ion implantation completely and efficiently.
The processing may be a process of forming an insulating film on the semiconductor region.
This enables an insulating film having desired properties, such as a gate oxide film, to be formed.
The processing may be a dry etching process for removing an insulating film from a top surface of the semiconductor region.
This enables the progression of the process of removing the insulating film to be controlled based on the result of in-line optical evaluation by using the fact that the change rate of the reflectance of the measurement light from the semiconductor region is influenced by the thickness of the insulating film.
Preferably, the semiconductor region is composed of n-type silicon.
Preferably, the exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
A first method of manufacturing a semiconductor device according to the present invention comprises: a first step of forming a substrate having a semiconductor region; a second step of evaluating an optical property of the semiconductor region; a third step of performing an etching process with respect to the semiconductor region; and a fourth step of controlling a condition for the etching process based on an optical property of the semiconductor region evaluated in the second step.
In accordance with the method, information on a structural disorder developed in the vicinity of the surface of the semiconductor region can be obtained by using the fact that light entering the semiconductor substrate reaches only a shallow portion. Based on the information, the depth of a damaged layer caused by etching in the semiconductor region and the degree of damage can be measured. Therefore, the manufacturing method of the present invention allows the properties of a semiconductor device to be set at desired values more precisely and with smaller variations than the conventional manufacturing method wherein an electric property is examined after the completion of the etching process and feedbacked to the conditions for etching.
The second step may include the steps of: supplying measurement light to the semiconductor region; intermittently supplying exciting light to the semiconductor region; and calculating a change rate of a reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
The method achieves the following effect. When the semiconductor region is irradiated with the exciting light, carriers are excited to produce an electric field. Due to the electric field, the reflectance of the measurement light changes in the presence and absence of the exciting light. The change rate varies depending on the intensity of the electric field and on the wavelength of the measurement light. If the semiconductor region contains a defect forming a center of recombination for carriers, the lifetimes of the excited carriers are reduced so that the electric field formed by the carriers has a reduced intensity. In other words, the change rate of reflectance in the presence and absence of the exciting light changes depending on the number of defects in the semiconductor region or the like, so that the change rate of the reflectance of the measurement light in the semiconductor region reflects the crystallographic state of the semiconductor region or the like. If a damaged layer is caused by etching, therefore, the depth thereof and the degree of damage can be obtained from the change rate of the reflectance of the measurement light. As a result, conditions for etching can be controlled properly.
The change rate of the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm, may be calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the damaged layer can be removed from the semiconductor region based on the information on the region of concern of a semiconductor device by using the fact that the measurement light of a wavelength in the visible region has the property of reaching a portion at a depth of several tens of nanometers from a surface of a semiconductor.
Preferably, the change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light is calculated in the step of calculating the change rate of the reflectance.
Preferably, the specified energy value of the measurement light is any value included in a range of 3.2 to 3.6 eV.
Preferably, the exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
Dry etching using a plasma may be performed in the third step.
This allows the degree of damage caused in the semiconductor region by the bombardment of ions during plasma processing to be obtained by optical evaluation performed with respect to the semiconductor region. The resulting semiconductor device has excellent properties due to processing using a plasma, which is generally used in the process of manufacturing a semiconductor device.
Prior to the second step, there may further be performed the steps of: depositing an interlayer insulating film on the semiconductor region of the substrate; and selectively removing the interlayer insulating film by plasma etching to form an opening reaching the semiconductor region, the second step may include evaluating an optical property of the semiconductor region exposed at a bottom surface of the opening, the third step may include performing light dry etching with respect to the semiconductor region exposed at the bottom surface of the opening to remove a damaged layer caused by the plasma etching, and the fourth step may include controlling a condition for the etching process based on a result of evaluating the optical property of the semiconductor region.
This ensures the removal of a damaged layer produced in the semiconductor region in forming the opening as the contact hole and prevents new damage from being caused by excessive light dry etching.
Regions of the semiconductor region to be formed with an element may be source/drain regions of an FET and the opening may be a contact hole reaching either of the source/drain regions.
In accordance with the method, the structural disorder in the source/drain regions is minimized, resulting in a FET with excellent properties.
A relationship between the optical property of the semiconductor region and a depth of the damaged layer may be predetermined by experiment and the fourth step may include obtaining the depth of the damaged layer from the optical property of the semiconductor region evaluated in the second step and performing light dry etching to remove a portion of the semiconductor region corresponding to the depth.
The method allows easy and prompt removal of the damaged layer from the semiconductor region by only one optical evaluation.
The fourth step may include controlling the condition for the etching process by reevaluating the optical property of the semiconductor region which varies with the progression of the light dry etching and comparing a result of reevaluation with a result of evaluation performed in the second step.
The method ensures the removal of a damaged layer produced in the semiconductor region in forming the opening as the contact hole and prevents new damage from being caused by excessive light dry etching.
Regions of the semiconductor region to be formed with an element may be source/drain regions of a FET and the opening may be a contact hole reaching either of the source/drain regions.
Prior to the second step, there may be performed the steps of: introducing an impurity at a high concentration into the semiconductor region of the substrate and depositing an interlayer insulating film on the semiconductor region; and selectively removing the interlayer insulating film by plasma etching to form an opening reaching the semiconductor region, the third step may include performing light dry etching with respect to the semiconductor region exposed at a bottom surface of the opening to remove a damaged layer caused by the plasma etching and predetermining a proper range of the change rate of the reflectance of the measurement light when an electric property of the semiconductor region is proper and the fourth step may include performing the light dry etching such that the change rate of the reflectance falls within the proper range.
This also ensures the removal of the damaged layer caused by dry etching.
The first step may include forming, as the semiconductor region, a first semiconductor region forming a part of a semiconductor element and a second semiconductor region to be subjected to optical evaluation, the second step may include evaluating the optical property of the second semiconductor region, the third step may include performing the etching process with respect to the first and second semiconductor regions simultaneously, and the fourth step may include controlling the condition for the etching process based on the result of evaluating the optical property of the second semiconductor region.
In accordance with the method, the area and impurity concentration of the second semiconductor region to be subjected to optical evaluation are optimized for optical evaluation, while the properties of the first semiconductor region to be formed with a semiconductor element are not practically affected thereby, which enables more accurate optical evaluation.
The first step may include adjusting an impurity concentration in the second semiconductor region to be higher than an impurity concentration in the first semiconductor region.
The method increases the sensitivity with which optical evaluation is performed so that higher-accuracy optical evaluation is performed more promptly.
Prior to the second step, there may be performed the step of introducing an impurity at a high concentration into the second semiconductor region of the substrate and depositing a gate insulating film and a conductive film for a gate electrode on the first and second semiconductor regions, the third step may include patterning the conductive film for a gate electrode and the gate insulating film by plasma etching and predetermining a proper range of a change rate of a reflectance of the measurement light when an electric property of the semiconductor region is proper and the fourth step may include performing the light dry etching such that the change rate of the reflectance falls within the proper range.
The method provides a FET with excellent properties, while removing damage caused to the source/drain regions in forming the gate electrode of the FET.
A silicon oxide film may be formed as the gate insulating film.
Preferably, the first step includes composing a portion of the semiconductor region to be subjected to optical evaluation of n-type silicon.
The second step may include evaluating the change rate of the reflectance of measurement light by using an ellipsometric spectroscope.
In accordance with the method, processing by etching can be controlled based on the result of in-line optical evaluation by using the ellipsometric spectrometer typically added to an apparatus for manufacturing a semiconductor device for measuring the thickness of an oxide film.
A second method of manufacturing a semiconductor device according to the present invention is for manufacturing a semiconductor device having a semiconductor region with a structural disorder developed therein, the method comprising the steps of: evaluating an optical property of the semiconductor region; and performing a heat treatment for recovering the semiconductor region from the structural disorder, while controlling a condition for the heat treatment based on the optical property of the semiconductor region evaluated in the foregoing step.
In accordance with the method, information on a structural disorder developed in the vicinity of the surface of the semiconductor region can be obtained by using the fact that light entering the semiconductor substrate reaches only a shallow portion. The heat treatment process can be controlled based on the information. Therefore, the semiconductor region can recover normal properties under optimum conditions for processing which will not adversely affect the properties of the semiconductor device. This is achieved by accurately sensing the structural disorder such as a crystallographic defect and a deviation from the normal state of electronic structure, without incurring lower sensitivity or increased noise due to the information from inside the semiconductor region.
The step of evaluating the optical property may include the steps of: supplying measurement light to the semiconductor region; intermittently supplying exciting light to the semiconductor region; and calculating a change rate of a reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
The method achieves the following effect. When the semiconductor region is irradiated with the exciting light, carriers are excited to produce an electric field. Due to the electric field, the reflectance of the measurement light changes in the presence and absence of the exciting light. The change rate varies depending on the intensity of the electric field and on the wavelength of the measurement light. If the semiconductor region contains a defect forming a center of recombination for carriers, the lifetimes of the excited carriers are reduced so that the electric field formed by the carriers has a reduced intensity. In other words, the change rate of reflectance in the presence and absence of the exciting light changes depending on the number of defects in the semiconductor region or the like, so that the change rate of the reflectance of the measurement light in the semiconductor region reflects the crystallographic state of the semiconductor region or the like. As a result, the range and degree of the structural disorder in the semiconductor region can be obtained from the change rate of the reflectance of the measurement light, which enables conditions for the heat treatment to be controlled properly.
The change rate of the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm, may be calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the recovery of the semiconductor region can be controlled based on the information on the region of concern of a semiconductor device by using the fact that the measurement light of a wavelength in the visible region has the property of reaching a portion at a depth of several tens of nanometers from a surface of a semiconductor.
Preferably, the change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light is calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the recovery of the semiconductor region can be controlled easily, promptly, and precisely by using the characteristic configuration of the spectrum indicative of the change rate of the reflectance which is increased or decreased depending on the wavelength of the measurement light.
Preferably, the specified energy value of the measurement light is any value included in a range of 3.2 to 3.6 eV.
Preferably, the exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
A proper range of the change rate of the reflectance of the measurement light when an electric property of the semiconductor region is proper may be predetermined and the heat treatment may be performed in the step of performing the heat treatment with respect to the semiconductor region such that the change rate of the reflectance of the measurement light falls within the proper range.
The method minimizes variations in the properties of the semiconductor region from lot to lot after the heat treatment.
A relationship between the change rate of the reflectance of the measurement light in the semiconductor region and an impurity concentration in the semiconductor region may be predetermined and the heat treatment may be performed with respect to the semiconductor device in the step of performing the heat treatment till the change rate of the reflectance of the measurement light in the semiconductor region reaches a value corresponding to a desired impurity concentration.
The method minimizes variations in impurity concentration and impurity diffusion in the semiconductor region from lot to lot. The resulting semiconductor device has an impurity concentration excellently distributed. Moreover, variations in the properties of individual wafers are negligible.
A first semiconductor region forming a part of a semiconductor element and a second semiconductor region to be subjected to optical evaluation may be preliminarily formed as the semiconductor region, the optical property of the second semiconductor region may be evaluated in the step of evaluating the optical property, and the first and second semiconductor regions may be simultaneously subjected to the heat treatment in the step of performing the heat treatment, while a condition for the heat treatment is controlled based on the result of evaluating the optical property of the second semiconductor region.
In accordance with the method, the area and impurity concentration of the second semiconductor region to be subjected to optical evaluation are optimized for optical evaluation, while the properties of the first semiconductor region to be formed with a semiconductor element are not practically affected thereby, which allows more accurate optical evaluation to be performed.
The first step may include adjusting an impurity concentration in the second semiconductor region to be higher than an impurity concentration in the first semiconductor region.
The method increases the sensitivity with which optical evaluation is performed so that higher-accuracy optical evaluation is performed more promptly.
Preferably, a portion of the semiconductor region to be subjected to optical evaluation is composed of n-type silicon.
Regions of the semiconductor region to be formed with a semiconductor element may be source/drain regions.
In accordance with the method, the heat treatment is performed to remove the structural disorder from the source/drain regions of a FET, thereby forming the FET with excellent properties.
The second step may include evaluating the change rate of the reflectance of the measurement light by using an ellipsometric spectroscope.
In accordance with the method, processing by etching can be controlled based on the result of in-line optical evaluation by using the ellipsometric spectrometer typically added to an apparatus for manufacturing a semiconductor device for measuring the thickness of an oxide film.
A third method of manufacturing a semiconductor device according to the present invention is for manufacturing a semiconductor device having a semiconductor region, the method comprising the steps of: evaluating an optical property of the semiconductor region; and introducing an impurity into the semiconductor region, while controlling a condition for the impurity introduction based on the optical property of the semiconductor region evaluated in the foregoing step.
In accordance with the method, information on a structural disorder developed in the vicinity of the surface of the semiconductor region can be obtained by using the fact that light entering the semiconductor substrate reaches only a shallow portion. Based on the information, the process of introducing an impurity can be controlled. Therefore, the semiconductor region can recover normal properties under optimum conditions for processing which will not adversely affect the properties of the semiconductor device. This is achieved by accurately sensing the structural disorder such as a crystallographic defect and a deviation from the normal state of electronic structure, without incurring lower sensitivity or increased noise due to the information from inside the semiconductor region.
The step of evaluating the optical property may include the steps of: supplying measurement light to the semiconductor region; intermittently supplying exciting light to the semiconductor region; and calculating a change rate of a reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
The method achieves the following effect. When the semiconductor region is irradiated with the exciting light, carriers are excited to produce an electric field. Due to the electric field, the reflectance of the measurement light changes in the presence and absence of the exciting light. The change rate varies depending on the intensity of the electric field and on the wavelength of the measurement light. If the semiconductor region contains a defect forming a center of recombination for carriers, the lifetimes of the excited carriers are reduced so that the electric field formed by the carriers has a reduced intensity. In other words, the change rate of reflectance in the presence and absence of the exciting light changes depending on the number of defects in the semiconductor region or the like, so that the change rate of the reflectance of the measurement light in the semiconductor region reflects the crystallographic state of the semiconductor region or the like. As a result, the range and degree of the structural disorder in the semiconductor region can be obtained from the change rate of the reflectance of the measurement light, which enables conditions for impurity introduction to be controlled properly.
The change rate of the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm, may be calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the introduction of the impurity into the semiconductor region can be controlled based on the information on the region of concern of a semiconductor device by using the fact that the measurement light of a wavelength in the visible region has the property of reaching a portion at a depth of several tens of nanometers from a surface of a semiconductor.
The change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light may be calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the recovery of the semiconductor region can be controlled easily, promptly, and precisely by using the characteristic configuration of the spectrum indicative of the change rate of the reflectance which is increased or decreased depending on the wavelength of the measurement light.
Preferably, the specified energy value of the measurement light is any value included in a range of 3.2 to 3.6 eV.
Preferably, the exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
A relationship between an amount of introduced impurity and the change rate of the reflectance of the measurement light may be predetermined by experiment and the impurity may be introduced in the step of introducing the impurity into the semiconductor region such that the change rate of the reflectance of the measurement light reaches a value corresponding to a desired amount of introduced impurity.
The method minimizes variations in impurity concentration and impurity diffusion in the semiconductor region from lot to lot. The resulting semiconductor device has an impurity concentration excellently distributed. Moreover, variations in the properties of individual wafers are negligible.
A first semiconductor region forming a part of a semiconductor element and a second semiconductor region to be subjected to optical evaluation may be preliminarily formed as the semiconductor region, the optical property of the second semiconductor region may be evaluated in the step of evaluating the optical property, and the impurity may be introduced into the first and second semiconductor regions simultaneously in the step of introducing the impurity, while a condition for the impurity introduction is controlled based on the result of evaluating the optical property of the second semiconductor region.
In accordance with the method, the area and impurity concentration of the second semiconductor region to be subjected to optical evaluation are optimized for optical evaluation, while the properties of the first semiconductor region to be formed with a semiconductor element are not practically affected thereby, which allows more accurate optical evaluation to be performed.
The third step may include introducing the impurity by plasma doping.
In accordance with the method, the change rate of reflectance gradually increases or decreases as the amount of introduced impurity increases in the case of plasma doping, so that controllability over the process of impurity introduction is improved.
Preferably, the impurity is an n-type impurity.
Regions of the semiconductor region to be formed with a semiconductor element may be source/drain regions.
In accordance with the method, respective impurity concentrations in the source/drain regions of a FET can be controlled with high precision, so that the resulting FET has excellent properties.
The second step may include evaluating the change rate of the reflectance of the measurement light by using an ellipsometric spectroscope.
In accordance with the method, processing by etching can be controlled based on the result of in-line optical evaluation by using the ellipsometric spectrometer typically added to an apparatus for manufacturing a semiconductor device for measuring the thickness of an oxide film.
A fourth method of manufacturing a semiconductor device according to the present invention comprises: a first step of forming a substrate having a semiconductor region; a second step of evaluating an optical property of the semiconductor region; a third step of forming a thin insulating film on the semiconductor region; and a fourth step of controlling a condition for the formation of the insulating film based on the optical property of the semiconductor region evaluated in the second step.
In accordance with the method, information on the properties of the insulating film overlying the semiconductor region can be obtained by using the fact that light entering the semiconductor substrate reaches only a shallow portion. The formation of the insulating film can be controlled based on the information. Therefore, the insulating film can be formed under optimum conditions without incurring lower sensitivity or increased noise due to the information from inside the semiconductor region. This is achieved by accurately judging the properties of the insulating film to be good or no good in the process of forming the insulating film.
The second step may include the steps of: supplying measurement light to the semiconductor region; intermittently supplying exciting light to the semiconductor region; and calculating a change rate of a reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
The method provides information on electric defects in the insulating film. Specifically, when the semiconductor region is irradiated with the exciting light, carriers are excited and the electric field changes as the number of carriers changes, so that the reflectance of the measurement light of specified wavelengths from the semiconductor region changes. In this case, if the insulating film has been formed on the semiconductor region, a defective layer for trapping the carriers is present in the surface layer of the semiconductor region, resulting in a reduced change rate of the reflectance of the measurement light. However, if a large number of defects (trapped electrons) are present in the insulating film, an increase in the intensity of the electric field in the adjacent semiconductor region is increased, so that the change rate of the reflectance of the measurement light is increased. Therefore, the insulating film is judged to be good or no good promptly and reliably based on the change rate of the reflectance of the measurement light.
The change rate of the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm, may be calculated in the step of calculating the change rate of the reflectance.
The method uses the measurement light of wavelengths shorter than those of visible light, thereby limiting the entering of the light into the semiconductor region to only a shallow portion and preventing degraded sensitivity due to information from the inside.
The change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light may be calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the formation of the insulating film can be controlled easily, promptly, and precisely by using the characteristic configuration of the spectrum indicative of the change rate of the reflectance which is increased or decreased depending on the wavelength of the measurement light.
Preferably, the specified energy value of the measurement light is any value included in a range of 3.2 to 3.6 eV.
Preferably, the exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
A proper range of the change rate of the reflectance of the measurement light when an electric property of the insulating film is proper may be predetermined by experiment and the fourth step may include forming the insulating film such that the change rate of the reflectance of the measurement light measured in the second step falls within the proper range.
The method minimizes variations in the electric property of the insulating films from lot to lot.
The second step may include measuring the change rate of the reflectance of the measurement light in the semiconductor region before the insulating film is formed thereon and the fourth step may include controlling a condition for the formation of the insulating film by remeasuring the change rate of the reflectance of the measurement light in the semiconductor region which varies with the progression of the formation of the insulating film and comparing a result of remeasurement with a result of measurement performed in the second step.
The method facilitates the formation of the insulating film having a desired electric property.
The first step may include forming, as the semiconductor region, a first semiconductor region forming a part of a semiconductor element and a second semiconductor region to be subjected to optical evaluation, the second step may include evaluating the optical property of the second semiconductor region, the third step may include forming the insulating film on the first and second semiconductor regions simultaneously, and the fourth step may include controlling a condition for the formation of the insulating film based on the result of evaluating the optical property of the second semiconductor region.
In accordance with the method, the area and impurity concentration of the second semiconductor region to be subjected to optical evaluation are optimized for optical evaluation, while the properties of the first semiconductor region to be formed with a semiconductor element are not practically affected thereby, which enables more accurate optical evaluation.
The first step may include adjusting an impurity concentration in the second semiconductor region to be higher than an impurity concentration in the first semiconductor region.
The method increases the sensitivity with which optical evaluation is performed so that higher-accuracy optical evaluation is performed more promptly.
Preferably, the first step may include composing a portion of the semiconductor region to be subjected to optical evaluation of n-type silicon.
After the fourth step, there may further be performed the step of judging the formed insulating film to be good or no good based on a relationship predetermined by experiment between the change rate of the reflectance of the measurement light and an electric property of the insulating film.
When the substrate is formed with a faulty insulating film, the method allows a new insulating film to be formed or the subsequent steps to be halted.
Preferably, a silicon oxide film is formed as the insulating film in the third step.
A gate insulating film may be formed as the insulating film in the third step.
The method improves the electric property of the gate insulating film which mainly determine the performance of the FET.
The second step may include evaluating the change rate of the reflectance of the measurement light by using an ellipsometric spectroscope.
In accordance with the method, the formation of the insulating film can be controlled based on the result of in-line optical evaluation by using the ellipsometric spectrometer typically added to an apparatus for manufacturing a semiconductor device for measuring the thickness of an oxide film.
A fifth method of manufacturing a semiconductor device according to the present invention comprises: a first step of forming a substrate having a semiconductor region and a thin insulating film overlying the semiconductor region; a second step of evaluating an optical property of the semiconductor region; a third step of removing the insulating film by dry etching; and a fourth step of controlling a condition for the removal of the insulating film based on the optical property of the semiconductor region evaluated in the second step.
In accordance with the method, information on the presence or absence of the insulating film on the semiconductor region can be obtained by using the fact that light entering the semiconductor substrate reaches only a shallow portion. Based on the information, the process of removing the insulating film can be controlled. Therefore, etching for removing the insulating film can be terminated with proper timing that does not damage the semiconductor region seriously without incurring lower sensitivity or increased noise due to the information from inside the semiconductor region.
The second step may include the steps of: supplying measurement light to the semiconductor region through the insulating film; intermittently supplying exciting light to the semiconductor region through the insulating film; and calculating a change rate of a reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light.
In accordance with the method, when the semiconductor region is irradiated with the exciting light, carriers are excited and the electric field changes as the number of carriers changes, so that the reflectance of the measurement light of given wavelengths from the semiconductor region changes. However, if the insulating film has been formed on the semiconductor region, a defective layer for trapping the carriers is present in the surface layer of the semiconductor region, resulting in a lower change rate of the reflectance of the measurement light. As a result, the progression of etching can be sensed promptly and reliably based on the change rate of the reflectance of the measurement light.
The change rate of the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm, may be calculated in the step of calculating the change rate of the reflectance.
The method uses the measurement light having wavelengths shorter than those of visible light, thereby limiting the entering of the light into the semiconductor region to only a shallow portion and preventing degraded sensitivity due to information from the inside.
The change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light may be calculated in the step of calculating the change rate of the reflectance.
In accordance with the method, the formation of the insulating film can be controlled easily, promptly, and precisely by using the characteristic configuration of the spectrum of the change rate of the reflectance which is increased or decreased depending on the wavelength of the measurement light.
Preferably, the specified energy value of the measurement light is any value included in a range of 3.2 to 3.6 eV.
Preferably, the exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
A proper range of the change rate of the reflectance of the measurement light when the removal of the insulating is properly completed may be predetermined and the fourth step may include performing dry etching with respect to the insulating film such that the change rate of the reflectance of the measurement light measured in the second step falls within the proper range.
The method minimizes variations in the damaged layers of the insulating films from lot to lot.
The second step may include measuring the change rate of the reflectance of the measurement light in the semiconductor region when the insulating film is formed thereon and the fourth step may include controlling a condition for the removal of the insulating film by remeasuring the change rate of the reflectance of the measurement light in the semiconductor region which varies with the progression of the removal of the insulating film and comparing a result of remeasurement with a result of measurement performed in the second step.
The method minimizes the damaged layer formed in the semiconductor region.
The first step may include forming, as the semiconductor region, a first semiconductor region forming a part of a semiconductor element and a second semiconductor region to be subjected to optical evaluation, the second step may include evaluating the optical property of the second semiconductor region, the third step may include performing an etching process with respect to the first and second semiconductor regions simultaneously, and the fourth step may include controlling a condition for the etching process based on the result of evaluating the optical property of the second semiconductor region.
In accordance with the method, the area and impurity concentration of the second semiconductor region to be subjected to optical evaluation are optimized for optical evaluation, while the properties of the first semiconductor region to be formed with a semiconductor element are not practically affected thereby, which enables more accurate optical evaluation.
The first step may include adjusting an impurity concentration in the second semiconductor region to be higher than an impurity concentration in the first semiconductor region.
Preferably, first step includes composing a portion of the semiconductor region to be subjected to optical evaluation of n-type silicon.
Preferably, a silicon oxide film is formed as the insulating film in the first step.
A gate insulating film may be formed as the insulating film in the first step.
The method minimizes the damaged layer formed in the semiconductor region which is to serve as the source/drain regions mainly determining the performance of the FET.
The first step may include forming a conductive film for a gate electrode on the gate insulating film and the third step may include sequentially pattering the conductive film for a gate electrode and the gate insulating film.
The method controls the removal of the insulating film and thereby minimizes the damaged layer formed in the semiconductor region which is to serve as the source/drain regions mainly determining the performance of the FET.
The second step may include evaluating the change rate of the reflectance of the measurement light by using an ellipsometric spectroscope.
In accordance with the method, the removal of the insulating film can be controlled based on the result of inline optical evaluation by using the ellipsometric spectrometer typically added to an apparatus for manufacturing a semiconductor device for measuring the thickness of an oxide film.
A method of controlling an apparatus for manufacturing a semiconductor device according to the present invention is a method of controlling an apparatus for manufacturing a semiconductor device comprising a chamber for containing a substrate having a semiconductor region, processing means for performing processing with respect to the substrate in the chamber, first light supplying means for intermittently supplying exciting light to the semiconductor region of the substrate placed in the chamber, a second light supplying means for supplying measurement light to the semiconductor region, and reflectance measuring means for measuring a reflectance of the measurement light supplied to the semiconductor region, the method comprising: a first step of supplying the measurement light to the semiconductor region; a second step of intermittently supplying the exciting light to the semiconductor region; a third step of calculating a change rate of the reflectance of the measurement light by dividing a difference between the respective reflectances of the measurement light in the presence and absence of the exciting light supplied to the semiconductor region by the reflectance of the measurement light in the absence of the exciting light; a fourth step of operating the processing means for a specified time till the change rate of the reflectance calculated in the third step reaches a specified value; and a fifth step of monitoring the specified time in the fourth step and outputting a signal for causing maintenance to be performed with respect to the apparatus for manufacturing the semiconductor device when the specified time exceeds a limit value.
The method allows monitoring of the processing time elapsed before the change rate of reflectance reaches a specified value, which is increased by the degradation of the components in the chamber. When the components in the chamber are degraded, therefore, effective maintenance can be performed with proper timing. The maintenance properly performed ensures optimum processing time and prevents the occurrence of a defect in the semiconductor region resulting from the excessive processing time.
The processing means may generate a plasma in the chamber and perform etching with respect to the semiconductor region by using the generated plasma.
The method enables proper maintenance of the chamber if the sensitivity with which the change rate of the reflectance of the measurement light is measured is reduced by a material deposited on the wall faces of the chamber during, e.g., plasma processing, while permitting plasma etching to be performed continuously in the chamber.
The processing means may generate a plasma in the chamber and perform light dry etching by using the generated plasma so as to remove a damaged layer caused by etching performed with respect to the semiconductor region.
The method enables proper maintenance of the chamber if the sensitivity with which the change rate of the reflectance of the measurement light is measured is reduced by a material deposited on the wall faces of the chamber during, e.g., plasma processing, while permitting dry etching for removing the damaged layer caused by plasma etching to be performed continuously in the chamber.
The processing means may introduce an impurity into the semiconductor region.
The method enables proper maintenance of the chamber if the sensitivity with which the change rate of the reflectance of the measurement light is measured is reduced by a material deposited on the wall faces of the chamber during the process of introducing the impurity, while permitting the process of introducing the impurity to be performed continuously.
The processing means may perform annealing after impurity ions are implanted in the semiconductor region.
The method enables proper maintenance of the chamber even if the components of the chamber are degraded by annealing performed at a high temperature, while permitting the annealing process for removing the structural disorder caused by ion implantation to be performed continuously.
The processing means may form a thin insulating film on the semiconductor region.
The method enables proper maintenance of the chamber if the sensitivity with which the change rate of the reflectance of the measurement light is measured is reduced by the degraded components of the chamber during, e.g., thermal oxidation, while permitting the insulating film to be formed continuously by thermal oxidation, CVD, or the like.
When a thin insulating film has been formed on the semiconductor region, the processing means may perform dry etching for removing the insulating film from a top surface of the semiconductor region.
The method enables proper maintenance of the chamber if the sensitivity with which the change rate of the reflectance of the measurement light is measured is reduced by a material deposited on the wall faces of the chamber during, e.g., plasma processing, while permitting dry etching for removing the damaged layer caused by plasma etching to be performed continuously.
The reflectance measuring means measures the reflectance of the measurement light of a wavelength of preferably 600 nm or less, and more preferably 300 to 600 nm.
The change rate of the reflectance of the measurement light at a specified energy value of the measurement light which provides a near extremal value in a spectrum of the change rate of the reflectance of the measurement light may be calculated in the step of calculating the change rate of the reflectance.
Preferably, the reflectance measuring means measures the reflectance of the reflected light of a specified wavelength by using an optical filter.
Preferably, the semiconductor region is composed of n-type silicon.
Preferably, exciting light is intermittently emitted at a frequency of 1 kHz or less in the step of supplying the exciting light.
A semiconductor device according to the present invention comprises: a substrate; a first semiconductor region provided in a top surface of the substrate to form a part of a semiconductor element to be formed on the substrate; and a second semiconductor region having an optical property monitored during processing performed in the first semiconductor region.
The arrangement allows monitoring of the state of the first semiconductor region varying with the progression of a variety of processing performed in the first semiconductor region with respect to a semiconductor wafer by using the optical property of the second semiconductor region. What results is a semiconductor device in which conditions and time for the variety of processing can be determined properly.
The second semiconductor region may be provided in a region other than a region to be formed with a semiconductor chip including the semiconductor element or, alternatively, in the region to be formed with the semiconductor chip including the semiconductor element.
The second semiconductor region may be composed of a semiconductor material to be used for monitoring by optical-modulation reflectance spectrophotometry.
Preferably, the second semiconductor region is composed of n-type silicon.